Although transmission of prions between species is generally inefficient, new research in the bank vole suggests that a small number of amino acid differences within the prion protein may have profound effects on the susceptibility of organisms to prions from other species (Watts JC et al. PLoS Pathog. 2014;10[4]:e1003990).

Unlike most mammals, the bank vole lacks a “species barrier” for prion transmission. To investigate the cause of this susceptibility, scientists from the University of California, San Francisco introduced the gene that encodes the normal bank vole prion protein into mice. In older age, some of the mice spontaneously developed neurologic illness. When young mice were exposed to toxic misfolded prions from 8 different species, all of them caused prion disease in the transgenic animals.